This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. As part of the chemical armamentarium used to combat invading pathogens, certain types of white blood cells produce reactive radicals. For instance, macrophages secrete superoxide and nitric oxide which combine to generate peroxynitrite, an agent that decomposes into species capable of damaging proteins, lipids, and DNA. With regard to DNA, guanine is particularly sensitive to peroxynitrite and numerous oxidized and nitrated derivatives have been identified. Furthermore, at sites of chronic inflammation, peroxynitrite is overproduced for prolonged periods of time. Indeed, a link between chronic inflammation and cancer has been established for inflammatory bowel syndrome ,colon cancer, gastric cancer, and Helicobacter pylori infection. Work both in vitro and in bacteria has shown that many of the peroxynitrite-induced DNA lesions are potently mutagenic and have varying degrees of toxicity. However, in order to understand fully the genetic consequences of peroxynitrite overproduction, and to unravel its contributions to cancer, we will examine the biological processing of these DNA lesions within a mammalian system.